Tire building machine

ABSTRACT

A tire building machine and method employing a tire building drum for receiving at least one ply of tire material having an edge overhanging an axial end of the drum, a bladder turn-up mechanism extending axially outwardly from the drum, an annular array of radially contractible ply-down fingers movable axially to and from a position encircling the overhanging ply edge, and an axially movable ring device operative first to effect radial contraction of the ply-down fingers to turn the ply edge down over the end of the drum, then to set a tire bead against the turned down ply edge at the end of the drum, and then to push the bladder of the turn-up mechanism when inflated to cause the ply edge to be progressively wrapped around the bead and then over the drum. In addition to a bead setting ring and a ply-down finger camming ring, the ring mechanism includes a contoured bladder control ring operative axially to push and radially to restrain the bladder, developed pressure in the bladder being reduced after contact is made with the control ring and then held at reduced pressure to allow the control ring to force the bladder to wrap around the bead and roll over the drum thereby to continue progressive wrapping of the ply edge around the bead and then over the drum with a bulge in the bladder forming in front of the axially inwardly moving control ring. Thereafter, the pressure in the bladder is further reduced, particularly in the case of long ply locks, to continue rolling of the bladder at the bulged portion to provide maximum ply lock with relatively low pressure sustained in the bladder. Finally, the bladder is reinflated while simultaneously retracting the control ring.

This is a divisional of co-pending application Ser. No. 570,650 filed onJan. 13, 1984 now U.S. Pat. No 4,584,038.

This invention relates generally to tire building machines and methodsand more particularly to an improved tire building machine and methodemploying a ply turn-down, bead setter and ply turn-up mechanism inoperative association with each axial end of a tire building drum.

BACKGROUND

In the manufacture of tires, it is conventional practice to apply one ormore tire plies in cylindrical form on a tire building drum with theedges of the plies extending axially beyond the ends of the drum, thento position inextensible tire beads at the ends of the drum, andthereafter to turn up the ply edges and stitch the same around the beadsand onto the outer surface of the tire ply material surrounding thedrum. Although most if not all presently used first or single stage tirebuilding machines and methods share this common practice, such machinesand methods nonetheless differ in many respects.

Many tire building machines and methods presently in use employ plyturn-up mechanisms incorporating one or two expandable bladders. Whenbrought into proper position at the end of the tire building drum andinflated, the bladder or bladders cause a previously turned down plyedge to be turned about a previously set bead at the end of the drum. Asis typical of these machines and methods, the bead is set in place by anaxially movable bead setting device which may also operate to contractan annular array of ply-down fingers when the latter are positionedaround the ply edge. As the bead setting device moves axially toward thedrum, the fingers are pivoted inwardly to turn the ply edge down overthe end of the drum to provide a shoulder of ply material against whichthe tire bead is pressed into place. For an example of one such tirebuilding machine and method, reference may be had to Cantarutti U.S.Pat. No. 3,438,832. As disclosed in such patent, the ply-down fingerswhen in an axially retracted position may provide a reaction surfaceoperative to cause one inflated bladder to force another inflatedbladder to wrap around the end of the drum.

In other tire building machines and methods, a single turn-up bladderhas been employed in cooperation with a bladder pusher to effect plyedge turn-up and wrapping. Typically, the bladder pusher is in the formof a ring mounted along with a bead setting device on a carriage whichactually moves to and from the drum. The carriage first moves towardsthe drum to set a bead carried by the bead setting device in properposition, then retracts to permit expansion of the turn-up bladder, andthen again moves toward the drum to engage the push the bladder over theend of the drum. Heretofore, such bladder pushers/bead setters have beenused with tire building drums which radially expand after application ofply material either to form a shoulder of ply material at the end of thedrum for bead placement thereagainst or to lock in place a beadpositioned by the bead setting device radially over the ply materialinwardly adjacent the end of the drum. For an example of the former,reference may be had to Appleby U.S. Pat. No. 3,078,204, whereas anexample of the latter can be seen in applicant's U.S. Pat. No. 4,343,671which also shows alternative usage of a dual bladder turn-up assembly.

Notwithstanding the advances that have been made in the tire buildingart, some of which are noted above, there still remains room forimprovement. Among existing needs are tighter wrapping of the plymaterial about the tire beads especially when long and hard durometerbead fillers are involved; compact wrapping with less air entrapment;less maintenance; reduction of electrical and fluid power hardware andcontrols; reduction of the amount of bladder expansion and pressurewhile providing a tight wrap; reduction of required cycle time; anduniformity of application to tires of both biased and radial plyconstructions.

SUMMARY OF THE INVENTION

To the achievement of the foregoing and other objects, the presentinvention provides a method of tightly wrapping the edge of tire plymaterial around a tire bead placed at the end of a tire building drumagainst the ply edge which extends axially beyond the drum end. Suchmethod is characterized by the steps of inflating to full or setpressure an annular bladder initially lying generally flat with itsaxially inner edge adjacent the drum end progressively to wrap and turnupwardly the ply edge around the tire bead; then axially inwardlypushing a portion of the bladder by an axially inwardly advancingbladder control ring, developed bladder pressure being reduced aftercontact is made and then held at reduced pressure to allow the controlring to force the bladder progressively to wrap around the bead and rollover the drum thereby to continue progressive wrapping of the ply edgearound the bead and over the drum, such control ring having an annularradial pusher surface terminating in a generally axially extending,cylindrical surface operative to rigidly radially constrain the bladderover a portion thereof overlying the bead and drum and behind a radiallyoutwardly bulged, axially inner end portion of the thusly rolledbladder; and then further reducing the pressure in the bladder tocontinue rolling of the bladder at the bulged portion to provide maximumply lock with relatively low pressure sustained in the bladder.Thereafter, the bladder is reinflated to pull the bladder away from theterminal end of the ply edge as by temporarily reestablishing the bulgewhile simultaneously retracting the control ring. As will beappreciated, a tight wrap may be obtained, even with beads having longand hard durometer fillers, without overstressing and stretching of thebladder and resultant reduction in bladder life.

Further in acordance with the method of the invention, amulti-functional ring device incorporating the above indicated bladdercontrol ring is utilized in various modes to effect not only theaforementioned bladder manipulation but also bead setting and ply-downfunctions. According to the invention, the ply edge extending axiallybeyond the drum may be folded down over the end or shoulder of the drumby a spring finger ply-down assembly which is moved axially inwardly tosurround the ply edge and then actuated by axial inward movement of thering device. The ring device also includes a bead setting ring whichoperates to hold and then place the bead against the down-turned plyedge at the shoulder of the drum. Thereafter, the ring device isretracted to clear the bladder and then again indexed axially inwardlyafter full inflation of the bladder to engage the control ring with theinflated bladder as described above and hereinafter in detail. As willbe seen, the axially inner edge of the bladder preferably is positionedto radially underlie the drum shoulder with its axially inner endportion extending axially beneath the full axial extent of the set beadagainst the tire material prior to inflation. As the bladder inflates tofull or set pressure, the ply edge is progressively wrapped around theunderside of the bead and turned upwardly. As the bladder is pushedaxially inwardly by the control ring after having been brought toreduced pressure, the bladder continues to roll over the beadprogressively to wrap the ply edge around the bead.

The present invention also provides a tire building machine for carryingout the method of the invention. Briefly, the machine comprises a tirebuilding drum for receiving one or more plies of tire material having anedge overhanging an axial end (usually both ends) of the drum, a bladderturn-up mechanism extending axially outwardly from the drum, an annulararray of radially contractible ply-down fingers movable axially to andfrom a position surrounding the overhanging ply edge, and an axiallymovable ring device operative first to effect radial contraction of theply-down fingers to turn the ply edge down over the end of the drum,then to set a bead against the turned down ply edge at the end of thedrum, and then to push the bladder of the turn-up mechanism wheninflated to cause the ply edge to be progressively and tightly wrappedaround the bead and over the drum. The ring device includes theaforementioned bladder control ring which may consist of a plurality ofannularly arranged, radially adjustable sectors.

To the accomplishment of the foregoing and related ends, the invention,then, comprises the features hereinafter fully described andparticularly pointed out in the claims, the following description andthe annexed drawings setting forth in detail a certain illustrativeembodiment of the invention, this being indicative, however, of but oneof the various ways in which the principles of the invention may beemployed.

BRIEF DESCRIPTION OF THE DRAWINGS

In the annexed drawings:

FIG. 1 is a fragmentary longitudinal section through a tire buildingmachine according to the present invention; and

FIGS. 2-10 are fragmentary longitudinal sections similar to FIG. 1 butillustrating the preferred sequence of operation of the tire buildingmachine of the present invention during the manufacture of a tire plyband.

DETAILED DESCRIPTION

Referring now in detail to the drawings and initially to FIG. 1, thereis illustrated generally at 20 a portion of a preferred form of tirebuilding machine according to the present invention which may be used inthe manufacture of conventional passenger or truck tires. The machineillustrated is operative as a first stage machine to construct tire plybands which may later be shaped to a toroid or tire shape on a secondstage machine where other tire components such as belts and/or treadsare assembled. It however will be appreciated that the present inventionmay be utilized with other types of tire building machines such as asingle stage machine wherein the tire ply band is both constructed andshaped.

The tire building machine 20 includes a tire building drum 21 mounted ona drum shaft 22 which may be conventionally supported and rotatablydriven by suitable means. The drum 21 may be of conventional radiallyexpandable type with suitable mechanisms being provided first to expandthe drum to an enlarged cylindrical configuration for proper placementof one or more tire plies thereon and later to contract the drum topermit removal of a finished tire ply band. Each axial end of the drummay be provided with an axially outwardly extending, circumferentialshoulder as seen as 23. In some applications, the drum may be expandedafter application of the tire plies.

The tire building machine 20 also includes an inboard assembly 26mounted adjacent one end of the tire building drum 21. Although notshown, the tire building machine also includes an outboard assembly atthe opposite end of the drum. Only the inboard assembly 26 is shown anddescribed hereinafter in detail inasmuch as the outboard assembly issubstantially identical in construction and operation to the inboardassembly. It is noted however that the outboard assembly as a unit orcomponents thereof may be mounted for axial separation from the drumshaft 22 to permit removal of a finished tire ply band from the drum aswell as placement of tire beads in the inboard and outboard assembliesprior to formation of another tire ply band.

The inboard assembly 26 comprises a bladder ply turn-up mechanism 28, aspring finger ply-down assembly 29 and a multi-functional ring device30. Such components are commonly supported for independent axialmovement on an annular support mounted on and concentric with the drumshaft 22. As shown, the support 31 has an axially elongate hub 32bearingmounted on the drum shaft 22 and an annular mounting flange 33extending radially outwardly from the axially outer end of the hub 32.As employed in the illustrated embodiment, the support 31 is fixedagainst both axial movement and rotation after adjustment for propershoulder set. Although not shown, suitable hardware may be employed toattach the support 31 to a fixed housing located to the right of FIG. 1in which a mount and drive for the drum shaft 22 may be housed. It isnoted, however, that the support 31 otherwise may be moved axially andeven rotated on the drum shaft if desired.

The bladder ply turn-up mechanism 28 is mounted on the support 31 foraxial movement towards and away from the tire building drum 21 by anannular shuttle 36 and a cylindrical shaft sleeve 37. The shuttle 36 isslidably received on the shaft sleeve 37 which is connected to thesupport hub 32 at the axially inner end of the latter. Axial movement ofthe shuttle 36 is obtained by actuation of an axially extendingpiston-cylinder assembly 38 which is connected between the shuttle 36and the mounting flange 33 of the support 31. By actuating the assembly38, the shuttle 36 may be moved axially toward and away from the drum asrequired during the tire building operation.

At its axially inner end (to the left in FIG. 1), the shuttle 36 hasattached thereto a radially extending plate 40 of the ply turn-upmechanism 28. The plate 40 has an annular radial projection 41 ofgenerally T-shape cross section, the stem of which extends slightlyaxially outwardly (to the right in FIG. 1) as well as radiallyoutwardly. The flanges of the T-shape projection 41 extend axially inopposite directions and terminate at radially inwardly projectingterminal ends which define annular grooves in which are received thebeads of an annular folded bladder 42. The axially inner and outer beadsof the bladder 42 respectively are retained in the grooves by axiallyinner and outer wedge rings 43 and 44 which are secured to oppositesides of the radial plate 40 by common fasteners, one being seen at 45.When deflated as seen in FIG. 1, the bladder 42 lies generally flat,having folded or looped portions 46 and 47 at its axially inner andouter circumferential edges, and is supported over substantially itsentire length by a cylindrical support can 48 mounted to the axiallyouter wedge ring 44. As shown, the support can is substantially radiallyinwardly offset from the outer diameter support surface of the drum whenthe latter is expanded.

Although the wedge rings 43 and 44 preferably are attached to the radialplate 40 by common fasteners 45, such rings may be otherwise configuredand mounted to the radial plate as by separate fasteners as seen inFIGS. 2-4. As further seen in FIG. 4, the radial plate 40 may beprovided with air passages, one being seen at 52. The air passages openoutwardly to the interior of the bladder 42 and each may be connected atits radially inner end to a respective axial bore 53 configured toreceive therein a fitting for coupling thereto of a respective airsupply (not shown) of the tire building machine. In a furtheralternative arrangement, a tubular bladder of the type seen inapplicant's U.S. Pat. No. 4,302,274 may be employed in a mannergenerally similar to that shown in such patent. Such bladder arrangementwould advantageously minimize required clamping hardware even beyond theclamping arrangement seen in FIG. 1.

Referring now to the spring finger ply-down assembly 29, such includesan annular array of spring fingers, each of which may be of the typeseen at 56 in FIG. 1. Each spring finger projects axially toward thetire building drum 21 and radially outwardly at an angle when in itsunflexed condition seen in FIG. 2. At their axially outer ends, thespring fingers are secured by a mounting ring assembly 57 to a supportring 58 which in turn is mounted for axial movement toward and away fromthe drum. For a detailed discussion of a preferred ring finger mountingarrangement, reference may be had to Yuhas U.S. Pat. No. 4,353,771. Asdisclosed therein, the spring fingers may be secured between two nestedrings which are constructed to interfit with each other and with eachfinger so that each finger may be inserted or removed without affectingadjacent fingers.

Any suitable means may be employed to mount the support ring 58 for theindicated axial movement. Preferably, the support ring 58 is coaxiallymounted for axial movement on the outer mounting ring 69 of thehereinafter described ring mounting assembly 66 as schematicallyindicated by the broken line 60. For example, the support ring may bemounted to the ring 69 by a bushing and guide rod assembly located at 12o'clock and a pair of axially extending piston-cylinder assembliesrespectively located at 3 and 9 o'clock. Consequently, axial movement ofthe support ring relative to the mounting assembly 66 may be obtained byactuation of such piston-cylinder assemblies interconnected between suchsupport ring and the mounting ring 69. Thus by actuation of suchpiston-cylinder assembly, the ply-down assembly 29 may be moved axiallytoward and away from the tire building drum 21 independently of themounting assembly 66 to which the ring device 30 is mounted as requiredduring the tire building operation. Also, a suitable adjustablemechanical stop may be provided to limit axial inward movement of theply-down assembly for proper positioning in relation to the drum 21 inthe below described manner.

The multi-functional ring device 30 also is supported on the support 31for axial movement by a pair of large, diametrically opposedpiston-cylinder assemblies, one being seen at 62 in FIG. 1. The cylinder63 of each assembly 62 is mounted to the outer axial side of the radialflange 33 with the piston rod 64 of each assembly extending axiallyinwardly through a tubular guide sleeve 65 for connection to a ringmounting assembly 66. The sleeve 65, which may be formed integrally withthe radial flange 33 as shown, is provided with bushings 67 whichreceive and support the piston rod 64 for sliding axial movement uponactuation of the assembly 62.

The ring mounting assembly 66 includes an axially outer mounting ring 69secured to the piston rod 64 of each assembly 62 and a radially innermounting ring 70 to which is secured an adaptor ring 71 of themultifunctional ring device 30. The outer and inner mounting rings 69and 70 are fastened together by suitable means (not shown) and havemating surfaces for squaring and concentrically positioning the adaptorring 71 relative to the axis of the drum shaft 22 or, more importantly,the axis of the tire building drum 21. As will be appreciated, theadaptor ring may be detachably secured to the inner mounting ring 70 forready removal and replacement of the multi-functional ring device 30 asdesired.

The functional components of the ring device 30 are a bead setting ring74, ply-down camming ring 75 and a bladder control ring 76, which areall fixedly secured to the adaptor ring 71. The bead setting ring 74,which is secured to the axially inner side of the adaptor ring 71, hasan axially inwardly extending annular projection adapted to receive andhold a tire bead seen at 77. In addition to a core of circumferentiallyinextensible wire elements, in some tire constructions the bead mayfurther have a long and hard durometer bead filler 78.

The ply-down camming ring 75 is set in place at the inner diameter ofthe bead setting ring 74 and adaptor ring 71. As seen in FIG. 1, suchring provides an annular bearing surface at the inner diameter of thering device 30 for operative engagement with the ply-down fingers 56 inthe manner hereinafter described. The ring may be made of any suitableplastic bearing material. The ring also may be relatively thick inradial dimension as seen at 75' in FIGS. 2 and 3 but this normally wouldrequire precision machining of the plastic for proper concentricactuation of the ply-down fingers 56. Such precision machining, however,may be eliminated by utilizing a relatively thin ring as seen in FIG. 1.When the fingers are retracted relative to the ring 75, they are heldclosed by such ring as seen in FIG. 1.

The bladder control ring 76 also is attached to the axially inner sideof the adaptor ring 71 but radially outwardly of the bead setting ring74. The bladder control ring has a contoured bladder pusher surfacecommencing at a point flush with the axial inner face of the beadsetting ring 74 and terminating at a substantially axially extendingcylindrical surface having an inner diameter somewhat greater than theouter diameter of the tire building drum when radially expanded. Theoperative relationship of the contoured bladder control ring to theturn-up bladder 42 and drum 21 will become more clear from the followingdiscussion of the operation of the tire building machine. The controlring may consist of a plurality of annularly arranged sectors fixedlyyet radially adjustably secured to the adaptor ring, such allowingradial adjustment of the control ring's pusher surface as needed toobtain optimum bladder control. The control ring also may have securedthereto an axially inwardly projecting extension ring assembly shown inbroken lines at 82 in FIG. 1. The extension ring assembly 82 includes anextension ring 83 mounted coaxially with and axially forward of thecontrol ring by axially extending brackets 84 secured at their axiallyouter ends to the outer diameter of the control ring (or sectorsthereof) by fasteners 85. The extension ring provides for extendedbladder rolling as may be desired in those applications requiring longsuch as 9" ply material overhangs. When employed, the extension ringwould serve to radially constrain the bladder forwardly of the controlring. As illustrated, the extension ring may have an inner diametersubstantially equal to or slightly greater than the maximum innerdiameter of the control ring. Of course, the particular dimensions ofthe extension ring and its extent of projection forwardly of the controlring may vary from application to application. As will be appreciated,such assembly constitutes an inexpensive optional retrofit for obtainingextended bladder rolling.

A preferred operational cycle of the tire building machine 20 will nowbe described with reference to FIG. 1 and the sequential views of FIGS.2-10. Although the operational steps will be described with respect tothe illustrated components at one end of the drum, the operationalsequence is generally applicable to the components at the other end ofthe drum. As is preferred, operation of like components at each end ofthe drum may be effected simultaneously by suitable controls.

Initially, the tire building machine 20 may be in the FIG. 1 position.As seen in FIG. 1, the tire bead 77 has already been placed on the beadsetting ring 74, this having necessitated radial contraction of the tirebuilding drum 21 to permit telescopic movement of the bead thereover.After the bead has been set in place, the drum can then be radiallyexpanded to its FIG. 1 position. As further shown in FIG. 1, theply-down assembly 29 is fully retracted such that the spring fingers 56are held closed in their flexed condition by the plastic ply-downcamming ring 75 of the ring device 30. As shown, the spring fingersterminate at a point radially inwardly of the bead setting ring to allowplacement of the tire bead on the latter.

After the tire building drum 21 has been radially expanded, the plyturn-up mechanism 28 then may be indexed axially towards the drum intoposition with the axially inner folded edge 46 of the bladder 42 locatedradially and axially inwardly of the drum shoulder. One or more plies oftire fabric material 79 may now be applied circumferentially around thedrum with a circumferential edge thereof overhanging (extending axiallybeyond) the end of the drum substantially as shown in FIG. 2. Aspreviously indicated, the fabric material might first be applied andthen the drum expanded.

At this time, the ply-down assembly 29 is indexed axially towards thedrum and relative to the ring device 30. As the inwardly flexed ends ofthe spring fingers 56 clear the plastic camming ring 75 in the ringdevice 30, the fingers will pivotally spring to their full opencondition seen in FIG. 2. Once open, further axial inward movement ofthe ply-down assembly will cause the spring fingers to encircle theoverhanging ply edge. In the illustrated embodiment, the ply-downassembly may be part way indexed to open the spring fingers and then thering device 30 moved axially toward the drum. As the ring devicecontinues to move towards the drum, the spring force of the fingers willcause the same to be carried with the ring device until the ply-downassembly moves into position and is stopped against further inwardmovement as by an adjustable mechanical stop. Once the ply-down assemblyhas stopped, inward advancement of the ring device thereover will causethe plastic camming ring therein to cammingly engage and radiallyinwardly pivot the spring fingers to turn the ply edge over the end ofthe drum as shown in FIG. 3. At the conclusion of the ply turn downoperation, the ring device continues to move axially inwardly to set thebead 77 carried by the bead setting ring 74 firmly against the end ofthe drum with turned-down ply material interposed between the bead anddrum shoulder 23. As will be appreciated, the bladder being directlysupported at its outer end on a reduced diameter cylindrical supportdrum provides additional clearance, in relation to known bladderturn-ups, for the plied down fabric furls or ruffles seen at 80 due tocord crowding and eliminates wrinkle problems commonly associated withthe use of spring fingers. That is, the radial spacing between the innerdiameter of the closed spring fingers and outer diameter of the deflatedbladder is selected to accommodate furling of the ply edge. Since suchfurling or waviness usually will be greatest at the distal end of theply edge, preferably the bladder is supported at its axially innerportion in a somewhat conical form as seen in FIG. 4.

After the ply edge has been turned down and the bead 77 set in place,the ring device 30 and ply-down assembly 29 and indexed axiallyoutwardly to retracted positions clearing the turn-up mechanism 28. Atthis time, air is supplied to the bladder 42 to expand the same from itsoriginal rest condition seen in FIG. 4 through the progressive stages ofinflation seen in FIGS. 5-7. As the bladder inflates from its FIG. 4condition, the ply edge is progressively wrapped tightly around theradially inner side of the bead and turned upwardly.

After the bladder attains maximum height or full pressure and with thebladder locked to the inside of the bead as seen in FIG. 7, the ringdevice 30 and ply-down assembly 29 once again are axially inwardlyadvanced to contact the control ring 76 with the bladder. Once thecontrol ring has contacted the bladder as seen in FIG. 7, developedpressure in the bladder is reduced and thereafter held at reducedpressure positively to lock the bladder to the control ring against anyslippage at the contact point as the control ring forces the bladder towrap around the tire bead and roll over the drum thereby to continueprogressive wrapping of the ply edge around the bead and then over thedrum. Prevention against slippage is necessary to ensure proper rollover and wrapping pressure. It is noted however that pressure reductionmay not be necessary in machines employing ring device actuators 62which are capable of generating high pushing forces.

After the control ring 76 reaches its axially inner position shown inFIG. 8, the axially inner end portion of the thusly rolled bladder willhave bulged radially outwardly in front of the control ring when at theintermediate bladder pressure as seen at 82 in FIG. 8, such control ringradially restraining the bladder over an intermediate portion thereofoverlying the bead and drum. As a result of such bulge, the bladder maynot be in pressed engagement with the distal end of a long ply edge asseen in FIG. 8. In order to complete progressive rolling of the bladderover the drum in such instance to its condition seen in FIG. 9, thebladder is further deflated to a relatively low air pressure. Thisobtains maximum ply lock with low pressure sustained in the bladder thenin the condition seen in FIG. 9. The bladder turn-up cycle may then becompleted by simultaneously reinflating the bladder and retracting thecontrol ring and finger ply-down assembly 29. Upon reinflation, thebladder once again bulges inwardly of the now retracting control ring asseen at 83 in FIG. 10 but only temporarily to move the bladder out ofcontact with the distal end of the ply edge. The amount of reinflationnormally will be dependent on the distance the bladder has been allowedto roll over the drum and such reinflation is particularly important toprevent the bladder from undoing what it previously had done as it lateris deflated. Such inflation, however, would not be necessary in thoseinstances where the bladder is not previously deflated to a relativelylow air pressure.

Finally, the bladder is fully deflated, the turn-up mechanism retractedaway from the tire building drum, and then the drum radially contractedto permit removal of the now finished tire ply band. Once the tire plyband is removed, the foregoing operational sequence can be repeated toconstruct a new tire ply band.

Although the invention has been shown and described with respect to apreferred embodiment, it is obvious that equivalent alterations andmodifications will occur to others skilled in the art upon the readingand understanding of this specification. The present invention includesall such equivalent alterations and modifications, and is limited onlyby the scope of the following claims.

I claim:
 1. A tire building machine comprising a tire building drum forreceiving at least one ply of tire material overhanging an axial end ofthe drum, a bladder turn-up mechanism extending axially outwardly fromthe drum, an annular array of radially contractible ply-down fingersmovable axially to and from a position encircling the overhanging plyedge, and a rigid ring device means axially moving first towards thedrum to effect radial contraction of the ply-down fingers to turn theply edge down over the end of the drum, then to set a tire bead carriedthereby against the turned down ply edge at the end of the drum, andthen, after having axially retracted to clear the bladder prior toinflation, axially moving the rigid ring device toward the drum to pushthe bladder of the turn-up mechanism when inflated to cause the ply edgeto be progressively wrapped around the bead and then over the drum.
 2. Amachine as set forth in claim 1, wherein said ring device means includesa bladder control ring operative axially to push said bladder wheninflated, and wherein developed pressure in said bladder is reducedafter contact is made with the control ring and then held at reducedpressure to allow the control ring to force the bladder to wrap aroundthe bead and roll over the drum thereby to continue progressive wrappingof the ply edge around the bead and then over the drum.
 3. A machine asset forth in claim 2, wherein said control ring has an annular radialpusher surface terminating in a generally axially extending, cylindricalsurface operative to rigidly radially constrain the bladder over aportion thereof overlying the bead and drum and behind a radiallyoutwardly bulged, axially inner end portion of the bladder after havingbeen rolled over the drum.
 4. A machine as set forth in claim 3, whereinpressure in the bladder is further reduced to continue rolling of thebladder at the bulged portion to provide maximum ply lock withrelatively low pressure sustained in the bladder.
 5. A machine as setforth in claim 3, wherein said control ring consists of a plurality ofannularly arranged, radially adjustable sectors.
 6. A machine as setforth in claim 1, wherein said bladder turn-up mechanism is mounted foraxial movement towards and away from the drum.
 7. A machine as set forthin claim 1, wherein said turn-up mechanism includes a generallycylindrical support on which said bladder substantially lies flat whendeflated, and means positioning said bladder with its axially inner edgelocated radially and axially inwardly of the drum end.
 8. A machine asset forth in claim 7, wherein said bladder, when deflated and positionedwith its axially inner edge located radially and axially inwardly of thedrum end, is radially inwardly offset from the drum end by an amountaccommodating furling of the ply edge resulting from the ply edge havingbeen turned down upon contraction of the ply-down fingers.
 9. A machineas set forth in claim 1, wherein said bladder has axially inner andouter beads secured by respective wedge rings in respective annulargrooves on opposite axial sides of an annular support in said turn-upmechanism, said wedge rings being secured to opposite sides of saidsupport by common fasteners.
 10. A machine as set forth in claim 1,wherein said ring device means is supported for axial movement by atleast one axially extending piston-cylinder assembly, said assemblybeing mounted at its cylinder on a support having an axially elongateguide sleeve provided with bushing means which receives and supports thepiston rod of such assembly for sliding axial movement.
 11. A machine asset forth in claim 1, wherein said ply-down fingers are carried by saidring device means yet movable axially with respect to said ring devicemeans for radial expansion and contraction.
 12. A machine as set forthin claim 3, further comprising an annular bladder constraining ringmounted coaxially with and axially forward of said control ring toprovide for extended bladder rolling.
 13. A tire building machinecomprising a tire building drum for receiving at least one ply of tirematerial overhanging an axial end of said drum, bead setting means forsetting a bead against the tire material at such axial end of said drum,an inflatable annular bladder extending axially outwardly from suchaxial end of said drum, means for inflating said bladder to turn theoverhanging ply edge up around the bead, an axially movable bladdercontrol ring having annular radial pusher surface means for engaging anaxially outer side of the bladder when inflated and a generallycylindrical, axially inwardly extending surface means radially outwardlyof said pusher surface means for radially constraining said bladder byengaging a radially outer side of the bladder when inflated, and meansfor axially moving said control ring towards said drum initially toengage the axially inner end of said bladder control ring against saidbladder when inflated at a contact point substantially below theinflated height of said bladder and then to force said bladder to wraparound the bead and roll over the drum to continue wrapping of the plyedge around the bead and then over the drum with no appreciable slippageoccurring between said bladder and said control ring at such initialpoint of contact.
 14. A machine as set forth in claim 13, wherein saidgenerally cylindrical, axially inwardly extending surface means isoperative to rigidly radially constrain the bladder over a portionthereof overlying the bead and drum after the bladder having been rolledover the drum.
 15. A machine as set forth in claim 13, wherein developedpressure in said bladder is reduced after such initial contact is madewith the control ring.
 16. A machine as set forth in claim 13, furthercomprising means for positioning said bladder with its axially inner endportion extending axially beneath the full axial extent of the set beadagainst the tire material.
 17. A machine as set forth in claim 13,wherein the axially inner end of said control ring is relatively narrowto the inflated height of said bladder.